Can view png, jpeg, gif, tiff, niff, sunraster, fbm, cmuraster,
pbm, faces, rle, xwd, vff, mcidas, vicar, pcx, gem, macpaint, xpm
and xbm files.  Can view images, put them on the root window, or
dump them.  Does a variety of processing, including: clipping,
dithering, depth reduction, zoom, brightening/darkening and merging.
